Mike Pelfrey pitched his first complete game in nearly three years, Carlos Beltran hit a mammoth home run and the New York Mets handed Dan Haren a rare beating Saturday night in a 6-1 victory over the Los Angeles Angels.

National League batting leader Jose Reyes sparked the offense with his latest big game from the leadoff spot and Jason Bay showed more signs of breaking out of his season-long slump.

Pelfrey (4-5) gave up five hits in his first win since May 10 at Colorado. He entered 0-2 in his previous six outings, though he pitched well in most of those.

The big right-hander struck out five and did not walk a batter for the third consecutive start. He threw a season-high 123 pitches in his third career complete game — the last one was Aug. 25, 2008, against Houston.

The only blemish was Mark Trumbo’s one-out homer in the sixth, and Pelfrey cruised home from there for New York’s third complete game of the year.

With the cheering crowd of 31,538 on its feet, Pelfrey retired Vernon Wells on an infield popup to end it.

Haren (6-5) entered with a 2.54 ERA, third-best in the AL, but had trouble holding runners in his shortest start of the season and didn’t get much help from his defense. New York stole four bases against him and catcher Hank Conger — two by Reyes — while building a 6-0 lead.

Beltran put the Mets in front with a two-out single in the third, then hit a two-run homer that chased Haren with nobody out in the fifth. Bay also had two hits, including an RBI single, and Reyes scored twice.

The Angels, who have thrived during interleague play the past few years, especially on the road, lost for the ninth time in 13 games overall.

Haren gave up seven hits and a season-high six runs in four-plus innings.

With the Mets already leading 3-0, Reyes drew a leadoff walk in the fifth and stole second.

Justin Turner smacked an RBI single to right and Beltran drove his 10th homer onto the Shea Bridge, a pedestrian walkway above the bullpens that sit beyond the right-center fence.

Estimated at 460 feet, it was one of the longest home runs a Mets player has hit at cavernous Citi Field, which opened in 2009. When he returned to the dugout, a smiling Beltran got an enthusiastic greeting from Reyes, and the Mets were on a roll.

NOTES: Asked about a report that Scott Boras is interested in representing him, Reyes said there’s “no chance” he is changing agents. The star shortstop, who can become a free agent after the season, said he’s happy with his current representative, Peter Greenberg. Reyes said Boras went to Colorado to see him earlier this year but they never even had a chance to meet. ... Mets manager Terry Collins rested Ruben Tejada, saying the 21-year-old second baseman looks a little tired. ... After a big game Friday night that included an outstanding catch, speedy CF Peter Bourjos was on the bench because Angels manager Mike Scioscia wanted Bobby Abreu’s streaking bat back in the lineup. Abreu, the regular DH, started in LF and Wells was in CF. ... 3B Alberto Callaspo (left hamstring) flied out as a pinch-hitter in the eighth. He should be ready to start when the team begins a three-game series Monday at Florida, Scioscia said. ... Scioscia said reliever Fernando Rodney (upper back strain) should be ready to come off the disabled list as soon as he’s eligible Friday. ... Actress and Mets fan Glenn Close sang the national anthem. She was at the ballpark raising awareness for her charity dedicated to mental health issues and posed for pictures with former Mets stars Tom Seaver, John Franco and Rusty Staub.